As known in the art, in vertical type wood shearing machines, the wood stock, which keeps decreasing in thickness, requires in order to fix it to the table supporting it, hooks or dogs of constantly smaller length, so as to maintain the hooks free from a portion of the wood stock to be reduced to sheets.
It is therefore necessary for the operator to stop the blade-holding and bar-carrying units during their feeding stroke, every time the fixing hooks have to be replaced by others of smaller length, since if this is not done the blade would strike the hooks and become damaged.
In order to avoid such a drawback, it has been proposed to automatically stop the blade-holding and bar-carrying units in two or more predetermined positions, by providing the wood shearing machine with two or more limit stops located on the guides of the units and adapted to function when actuated by corresponding microswitches. The latter become sensitive when coming into contact with a respective box, originally containing a set of hooks, when it is empty and the hooks are mounted on the machine.
It may be readily understood that the assembly, comprising the microswitches/limit stops and boxes to collect the hooks not being used, is a mechanically and electrically complex assembly which therefore does not ensure sufficient safety.